# l1-ecs-service — ECS Fargate service primitive (multi-resource L1)

An L1 module for an ECS Fargate service (task definition + service).
Substrate-agnostic (the IR types are `aws:ecs:task_definition` and
`aws:ecs:service`, not Terraform resource types). This is a
multi-resource L1: the interface declares the group's inputs/outputs
plus a `resources` array listing the IR types it emits. The IR instance
(Phase 14/15) will have multiple `resources` entries all with
`module: "l1-ecs-service@1.0.0"`.

## Interface (the IR-typed contract)

See `interface.json`: inputs `image` (string, ECR image URL), `port`
(number), `cpu` (number, default 256), `memory` (number, default 512),
`env` (optional JSON map string), `cluster_arn` (arn, ref to
l1-ecs-cluster), `subnets` (string, ref to l1-vpc), `security_group`
(string), `lb_target_group_arn` (arn, optional, ref to l1-alb), `region`
(string); outputs `service_arn` (arn) + `task_def_arn` (arn); no NFRs.

The `resources` array lists the emitted IR types:

- `aws:ecs:task_definition` — Fargate task definition. The adapter
  jsonencodes `image`/`port`/`env` into `container_definitions`.
- `aws:ecs:service` — Fargate service running the task definition in the
  cluster + subnets (+ optional ALB target group wiring).

## IR → Terraform mapping (performed by the adapter)

The Terraform adapter (`adapters/terraform/adapter.py`) translates each
emitted IR resource to Terraform:

| IR | Terraform |
|----|-----------|
| `resource.type = aws:ecs:task_definition` | `resource "aws_ecs_task_definition" "<id>" { ... }` |
| `resource.inputs.image` + `port` + `env` | `container_definitions = jsonencode(...)` (adapter-built) |
| `resource.inputs.cpu` | `cpu = <value>` arg |
| `resource.inputs.memory` | `memory = <value>` arg |
| `resource.outputs.task_def_arn` | `output "task_def_arn" { value = aws_ecs_task_definition.<id>.arn }` |
| `resource.type = aws:ecs:service` | `resource "aws_ecs_service" "<id>" { ... }` |
| `resource.inputs.cluster_arn` | `cluster = <value>` arg (identity) |
| `resource.inputs.subnets` | `network_configuration { subnets = [...] }` (emit as-is) |
| `resource.inputs.security_group` | `network_configuration { security_groups = [...] }` (emit as-is) |
| `resource.inputs.lb_target_group_arn` | `load_balancer { target_group_arn = <value> }` (emit as-is) |
| `resource.outputs.service_arn` | `output "service_arn" { value = aws_ecs_service.<id>.id }` |

The adapter is a thin layer (ARCHITECTURE.md §12.2); it does not own L1
content — it only translates. The `container_definitions` JSON is built
by the adapter from the IR `image`/`port`/`env` inputs (the one
transformation the adapter owns for ECS task definitions).

## Versioning (W3.D)

`1.0.0` — interface MAJOR, behavior MINOR, lifecycle PATCH. MAJOR bumps
require a new registry entry (immutable publication); old entries enter
a 12-month deprecation window.